Friday, July 05, 2013

Excessive Heat Watches This Weekend

The immediate Delaware Valley is under an excessive heat watch for Saturday afternoon and Sunday.  The watch does not include the upper halves of Bucks, Montgomery, and Chester Counties, nor does it include South Jersey  outside of the immediate suburban counties just across the river from the city.

The heat watches are prompted by the combination of heat and dew point yielding potential peak heat index values around 100 degrees in the afternoon hours tomorrow and also on Sunday...although with the threat of a few storms around Sunday afternoon it's possible we don't get quite get to 100 degree heat index values then.  More on Sunday (and Monday's) thunder threat later on.

As for tomorrow's heat -- temperatures should get into the mid 90's in most locations tomorrow afternoon. This, combined with dew points around 70, should get us pretty close to 100 degree heat index values. Some spots will yield higher dew points and thus higher heat index values but this is a blend of the NAM and GFS MOS and what that would spit out for a resulting heat index value. The "raw" data from the models suggest higher dew points than the MOS output but the raw data overdid yesterday afternoon by a few degrees...if by some chance those higher dew points do verify, heat index values will be a bit higher as a result.

If you think Saturday and Sunday are bad...just remember that in 2010 and 2012 it was hotter...